Sequence of Operation LGM/LCM156 & 180U
1 - Line voltage from TB13 energizes transformer T1 and T18. Transformer T1 and T18 provides 24VACpower to the main controller A55. The transformers also
provide 24VAC power to the unit cooling, heating and blower controls and thermostat
ECONOMIZER OPERATION
2 -
3 -
1ST STAGE COOLING
4 - First stage cooling demand energizes Y1 and G in the thermostat. G energizes blower, if blower is not already running (see step 3).
5 - 24VAC is routed to the A55 Unit Controller. After A55 proves N.C. low pressure switch S87 , high pressure switch S4 and high temperature limits S5
compressor contactor K1 is energized.
N.O. contacts K1-1 close energizing compressor B1.
7 - A178 energizes outdoor fans B21 and B22.
8 -
2ND STAGE COOLING
Second stage cooling demand energizes Y2.
10 -
11 - N.O. K2 closes energizing compressor B2 and de-energizing crankcase heater HR2.
12 - N.O. K14 closes energizing compressor B13, de-energizing HR5.
13 - A178 energizes outdoor fans B4 and B5.
BLOWER OPERATION With By Pass
1 -
2 - K203-1 N.C. contacts open to de-energize K3 relay coil. K3 contacts open to interrupt power to B3 blower motor through K3 N.O. relay contacts.
3 -
BLOWER OPERATION No By-Pass
1 -
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